Production of alloys capable of being forged and hardened



Patented July 11, 1933 UNITED STATES PATENT OFFICE WERN R STAHLWERKE AKTIEN GESELLSOHAI FT, F DUSSELDOBF, GERMANY raonuc'rrou or armors carnal. 101+ name ro'aenn m HARDENED No Drawing. Application The fundamental composition of a high speed steel has remained unaltered since its evolution.

hardening of the steel, the hi quenching 0.60.9% C,.1220% W0, 3'-6% Cr, balance iron with the usual impurities, Latterly, in addition to' the above ingredients, up to 2% V and 25% Co are added. Yet with all modifications the carbon content remained unaltered if indeed it had' not been increased for special purposes (rifleled steel) In this connection the carbon content has always been considered a necessary condition for the h' degree of hardness being obtained imme iately after from high temperatures.

According to the invention, however, one succeeds in producing alloys of the high slpueed steel type which in their behaviour lly show the characteristics of the high speed steel, yethave special advantages over the known high speed steels. These new alloys difler from the high speed alloys in as much as they are practically free fromioarbon that is to say they contain carbon only in traces. These alloys consist of iron, 5 to 35%tungsten or of molybdenum or of tungsten and molybdenum and 5 to 50% of cobalt. These alloys are subjected to a difierent heat treatment than the carbon containing alloys hitherto used which were hardened merely by quenching. In contradistinction' thereto the alloys according to the invention are hardened by precipitation hardening. For

1 as well as the hard metal alloys of high cathis purpose the alloys are first quenched from high temperatures. Yet by this quenching operation they are not hardened, but are in this state capable of being worked. It is 0111 by reannealing them at temperatures of about 400800 C. that they. subsequently take up the high degree of hardness necessary for technical purposes. Thus, as far as the heat treatment is concerned, the new alloys differ fundamentally from the heretofore customary high speed steels and offer decided advantages over the high speed steel pacity. First of all they are capable of be- .ingfor ed whereas the hard metals, such as those 0 the stellite type, may be used only in the form of castings and machined'only filed Iarch 31, 1931-, Serial lio. 528,777, and in Germany April 8, 1980.

by grinding. Furthermore, they are capable KfiS'l'EB, OF DOBTMUNDQGEBHANY, ASSIGNOR TO THE FIRM VEREHTIGTE 1 of being worked after quenching. T1115,

means that the final shaping may be efiected subsequent to quenching whereas in the case of the high speed steel, it has to be carried out prior to the quenching operation. In this way one succeeds in preventing the finished tool from being subjected to the extraordinary high temperatures of 1200-1300 C. which are liable to cause an undesired distortion of the tool. On the other hand, by the subsequent reheating which causes only the high degree of hardness, ume are produced of a size sufficiently small to be ractically negligible. Hence it is made possi 1e to manufacture thetools in a very clean state, since, chined, they may be pickled and subsequently reannealed in' a neutral or even in a decarburizing atmosphere. From the facts mentioned it will be seen that decided tech-. nical improvements on the present practice of manufacturing tools may thus be accomplished.

One method of producing these new cutting alloys is shown by the ,following example The alloy, in addition to the usual impurities (sulphur and phosphorus), contains 15% of tungsten, 30% of cobalt, 0.08% of carbon, 0.1% of silicon, 0.6% ofmanganese,

balance iron. It has been quenched in oil at 1250 C. and reannealed at 650 C; for one hour. The hardness thus obtained was .710 units Brinell. It speaks well for the chiplped. T e tungsten content of the alloy may be changes in volafter having been mareplaced partly or wholly by molybdenum.

The cobalt content may be replaced partly or wholly by chromium, manganese, vanadium and other metals. It is to be under-' stood that such further metals acting in the same manner as cobalt with respect to the phenomena dealt with by the present invention are comprised by the term cobalt used in the claim. Small amounts of rare metals such as titanium, zirconium, uranium and others may also be added without departing from the spirit of the invention.

The composition and the heat treatment, as far as the height of the quenchingand reheating temperatures is concerned, de-

pends upon the requirements that have to bemet by the tool to be manufactured. The alloys may be used for the manufacture of tools of widely difierent types. Their use is not limited to chipping tools but may be extended to those which are subjected to wear, among which the following may be mentioned by way of example: cutting knives, files, drawing rings, drawing nozzles etc.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A substantially carbon free tool steel alloy containing 5 to of tun sten and in addition 5 to of cobalt, the balance consisting substantially of iron, said alloy having been hardened by precipitation hardening by heating the alloy between 900 C. and the melting point, rapidly cooling and heating between 400 and 800 C.

2. A substantially carbon free tool steel alloy containing 5 to 35% of molybdenum and in addition 5 to 50% of cobalt, the balance consisting substantially of iron, said alloy having been hardened by precipitation hardening by heating the 'alloy between 900 C. and the melting point, rapidly cooling and heating between 400 and 800 C.

3. A substantially carbon free tool steel allow containing 5 to 35% of tungsten and molybdenum and in addition 5 to 50% of cobalt, the balance consisting substantially of iron, said alloy having been hardened by precipitation hardening by heating the alloy between 900 C. and themelting point, rapidly cooling and heating between 400. and 800 C.

4. A tool steel alloy containing about 0.08% carbon, 5 to 35% of metal selected from a group consisting of tungsten and molybdenum, and in addition 5 to 50% cobalt and the balance substantially iron, said alloy having a Brinell'hardness of about 710 obtained by precipitation hardening.

In testimony whereof I afiix my signature.

WERNER KGSTER. 

